Specifications of wire and cable trays

Wires used in cable trays are typically tray-rated cables such as Type TC, TC-ER, or ITC, designed for durability, flame resistance, and compliance with NEC standards.

Types of Tray Cables

Type T

C (Tray Cable): Factory-assembled cables with two or more insulated conductors under a non-metallic jacket, rated for 600 volts. Suitable for power, control, and signal circuits in cable trays, raceways, and outdoor locations when supported.

T

C cables are UL listed and may be used in Class 1, Division 2 hazardous locations. Type TC-ER (Exposed Run): Similar to TC but designed to transition from the tray to equipment for distances up to six feet without continuous support, meeting crush and impact requirements per UL 1569.

Type IT

C (Instrumentation Tray Cable): Used for instrumentation and control, available in shielded or unshielded constructions, sometimes with metal armor, for sensitive signal applications.

Voltage Ratings and Insulation

Voltage Ratings: Commonly 300V (PLTC) or 600V (TC, TC-ER) depending on application. Insulation and Jacket: Durable outer jackets resist sunlight, moisture, oil, and mechanical damage. Flame-retardant construction is required to meet UL and NEC fire safety standards.

Armor: Some cables include metal armor over individual conductors for additional mechanical protection.

Conductor Sizes

American Wire Gauge (AWG) is used to specify conductor size. Power circuits typically use 14 AWG and larger, while control or instrumentation circuits may use 16–18 AWG. Proper sizing ensures adequate ampacity, minimizes voltage drop, and maintains installation flexibility.

Installation Considerations

Cables must be UL listed and marked as cable tray rated. Fill capacity, securing, and support must comply with NEC Article 392. Ladder trays are preferred for heat dissipation, while solid-bottom trays are used where EMI shielding or protection from falling objects is needed.

TC-ER cables allow short unsupported runs to equipment, but standard TC cables must remain within the tray or raceway.

Summary

When selecting wires for cable trays, ensure they are tray-rated (TC, TC-ER, ITC), have the correct voltage rating, conductor size, and insulation type, and comply with NEC Article 392. Consider environmental conditions, mechanical protection, and whether the cable will transition outside the tray to determine if TC-ER or armored cables are required.